Birds, Brains, and Boats: The Harvey Karten Story

To be honest, it wasn’t how I expected to find Dr. Harvey J. Karten, neuroscience Professor Emeritus and recent inductee to the National Academy of the Sciences. But when I open the door his office on a bright San Diego afternoon, he is sitting in front of three monitors, hard at work. With zebrafish histological images on one screen, a neuron tracing program, Neurolucida, on the far display, and an image of his late wife positioned in the middle, it’s clear I’ve walked into a room where he spends much of his time. In the foreground I find a leaning stack of white slide boxes and a black baseball cap, while jumbles of cords, and hard drives. Stacks of countless papers lurk in the background. For Harvey, the game is very much still afoot.

Harvey Karten is an unsung hero in neuroscience, and a proud spokesperson for the non-mammalian vertebrates that are often overlooked in a field he dearly loves. What follows is just a glimpse into the insight and knowledge that he has gained from over 50 years in neuroscience.

Beginnings

Thinking back to his start as a scientist, Harvey comments, “I was a nerdy kid. I was a really nerdy kid.” Growing up during the Second World War in the New York City area, Harvey tinkered with electronics and read Science Illustrated magazines that his mother brought home from her candy store. High school wasn’t his forte though, “I was nerdy, but not a very good student.” Originally considering going to graduate school for chemistry, Harvey ended up getting into medical school. At the time, there really weren’t many PhD programs, and going into science was not a popular path.

Throughout medical school, the thought of working in a lab hadn’t faded. Harvey skipped out of his Colorado residency early and jumped into a 18-month research position at Walter Reed Army Institute of Research in D.C.” Without much previous research experience, he was given some grant money, and a microscope. In a prescient introduction to anatomy, it was love at first slide.

The colors, the anatomical esthetics, the technology of optics, interesting unknown pathways of unknown function, imagining how I might sort it all out. I was seeing things in the brain for the first time in my life, and imagined that every day was another “first ascent” in mountaineering. I realized that for the first time in my life, I could do exactly what my curiosity might drive me to. No grades, no supervisor convinced that they knew the only right way to do things.

On crutches from a recent skiing accident, Harvey spent those initial eight hours peering through the oculars at slides of a cat brain, unraveling the connections of a bit of white matter beneath the thalamus, the “fields of Forel.” It quickly became clear that he would not return to clinical medicine. Eighteen months turned into three years, and the medical school had to constantly check to see if Harvey was ever coming back. Luckily for neuroscience – he was not.

Surrounded by some of the most influential names in early neuroscience – Walle Nauta, William Hodos, Bob Galambos, and David Hubel – Harvey found himself at the forefront of a burgeoning field. Nauta enabled Harvey to pursue his own insights, and fresh ideas were always “grist for the mill.” With plentiful funding, scientists at Walter Reed were free to follow their intuition: “It was a toolbox to play in… If you decided to do something offbeat, there was no question about it.” The difference between exploratory, unrestricted science in the 1960s and our 2015 prescriptions for science (written in the form of grants) becomes very clear. “Money was pretty readily available. It made a big difference in willingness to invest in long, long-term projects,” Harvey reflects.

He describes today’s scientific culture as robotized and industrialized, where research is primarily done in C. elegans, Drosophila, mice, and maybe humans – “as if that’s some sort of evolutionary sequence.” Fortunately, in the 1960s, Harvey was able to explore a variety of different nervous systems; and as a pioneer in the burgeoning field of neuroscience, explore he did.

The unexplored and underrated bird brain

Although the original plan was to move on to electrophysiology, the anatomy side of things led Harvey to more questions than answers:

Why do we think cortex is so fantastic? What does it do that is unique in a mouse, that a bird can’t do? … The literature was filled with the idea that the mammalian brain was really something special – it’s got cortex. Well, how did non-mammals deal with auditory and visual cues?

Harvey found ethological perspectives of the brain to be much more relevant to understanding nervous systems, but at the time there was not much research on the neural basis of such observations, such as the different ways that birds and mammals find their food. Like every great career in science, Harvey’s began with questions.

At a glance, human and bird brains look quite different. But when you consider their developmental and evolutionary trajectories, they are actually quite similar. Harvey showed that birds had very similar visual system organization to mammals, despite the fact that they do not have an elaborate cortex.

And so, the bird science began. The first challenge: stabilize a pigeon’s head, in order to study it and ultimately create a bird brain atlas. Equipped with previous knowledge of cat cortex, Harvey found himself in a unique position to understand the bird neuroanatomy and compare it to that of mammals: “What we discovered was that the more we looked, the more and more it was looking like a mammalian brain.”

Throughout our conversation, it’s clear that Harvey hasn’t stopped thinking about neuroanatomy since the first day he sat down at the microscope. We wind through various brain regions, cell types, and pathways, from the thalamic nucleus rotundus to the neostriatum intermediale; there are moments where I have to pause and make sure he’s speaking English, not Latin. Many of these pathways were first described by Harvey and his colleagues and have since been observed in a variety of different species. Harvey’s face lights up when he mentions that many people are just starting to confirm his original ideas, despite initial skepticism:

It’s taken a long time and a lot of techniques. When I published that paper I thought, the story is over, let’s go on to the next question in this whole thing: what’s the molecular basis of this? And nobody was interested in that; we didn’t have the tools to do it so I just kept working on related things. Solved the problem of the evolution of stereopsis … I don’t know if you know the solution to the problem?”

I admit, I don’t. “It’s really, really simple,” he assures me. Without pause, he dives into an explanation about how retinal pathways are totally crossed in birds and most non-mammalian species.

For a long time there was a prevailing notion that birds simply did not have the ability to combine input from both eyes, a phenomenon known as stereopsis. As it turns out, birds have additional nuclei after the thalamus, where retinal inputs are combined; similar organization as in mammals, but the crossing happens one synapse later. After that, everything is the same. “So when you reach conclusions about how drastically different things are, you better be damn sure that they are different before you go off preaching the absolute word of truth on these things.”

Harvey knows a tremendous amount about bird brains, but doesn’t have a favorite (they all are interesting for their own reasons), and doesn’t consider himself a true bird watcher. Rather than try to spot a variety of birds, he goes out and watches birds for hours at a time, considering how their brains allow them to accomplish things.

“For instance,” he pauses, “how much time do you have?!” Plenty of time, I assure. “I’m going to make you into a sparrow,” he says.

Harvey places a tiny ball of paper on the table, and tells me to cover one eye, and grab the paper. I carefully stretch my hand out, awkwardly grabbing it, and Harvey quickly remarks, ”ten sparrows would have eaten that grain of seed before you!” We repeat the experiment with both eyes open, and not surprisingly, it takes significantly less time. Ergo, birds must have stereopsis. Although we almost always photograph them as if they’re in a criminal line-up, looking directly left or right, almost every bird has binocular overlap in at least some area of their visual system. I’m officially convinced.

In addition to his work with the avian brain, Harvey sought to popularize the idea that cortex had many different cell types, and was not uniform across areas or species.

We move on to explore how egrets, owls, ducks, and starlings feed, each of them with a different zone of stereopsis, depending on the way that they eat. If your food is below you, the binocular zone is very likely towards the bottom of your visual field – that’s where you need to see in better detail. The same is true of reptiles. If you watch a chameleon, you’ll see it pop its wandering eyes into place when it begins to climb. Harvey has spent countless hours watching, and he recommends I do the same: “You’re a biologist, get out in the field! It’s really worth it.”

Unpopular views

After his paper in 1969, Harvey became quite the rabble-rouser. Birds had a similar visual system organization to mammals? Rubbish, they said. Holding a minority perspective gave Harvey a tremendous amount of insight into how science operates:

“We tend to build a model, and then we do the worst possible thing: we believe the model as if it’s true, even when more research needs to be done.”

In addition to his own work disproving ideas that bird brains were radically different, he cites competing ideas about the diversity and development of the cortex that have largely been overlooked due to the dominant notion that cortical development occurs from the inside-out, or “radially.” In his 1969 paper, he proposed a way that neurons might migrate tangentially, rather than radially. Indeed, recent studies have shown this to be the case in certain brain regions.

Furthermore, he had a prescient idea: if we only had the molecular fingerprint of these neural connections, we might be able to tease them apart even further. At the time, even the idea of diverse cell types in the brain was quite radical. Regardless, Harvey became convinced through his observations that cortex contained hundreds, perhaps thousands of different cell types, which we now know to be accurate. More and more, researchers are realizing that cortex is not uniform, and it certainly does not all form in the same way. Since the 1960s, Harvey has been a key player in these debates.

An evolving field

And still, fifty years later, Harvey is relentlessly involved in the field, working to generate better anatomical images and well-organized repositories of data as part of the neuroinformatics movement. He contributes to several efforts to make anatomical images more easily accessible, including BrainMaps.org. In his opinion, it’s important to make the original data available, so that people can check your interpretation. “Metadata,” what we normally publish, is inevitably biased.

Looking forward, Harvey is excited by new technologies allowing us to define cell types and circuits, explore evolutionary histories, and distinguish cell transformations at a molecular level. As far as what’s coming next, “it’s anybody’s guess,” he says, “your guess is probably better than mine. Young people have better vision.” Sure, I say, but I assure him that his perspective must give him a speculative advantage. “Oh bullshit,” he shakes his head, “No, no. Perspective does you a little bit, but imagination gets you a lot further.”

Advice for those of us who aren’t Harvey Karten

When I ask Harvey what I should be doing as a budding scientist, he urges me to figure out everything that my advisor is doing wrong. Be critical, he says:

“When you’re young, you have to say everyone else is full of shit. You don’t say it out loud, you know, because you need a letter of recommendation or something like that, but privately you should always say everyone is full of shit.”

He goes on to describe how several researchers really pushed the idea that acetylcholine was the primary neurotransmitter in the nervous system, because it was what they had observed at the neuromuscular junction. Now we know that many different neurotransmitters and modulators work in a carefully orchestrated balance in the brain, each playing a part.

Along the same lines, Harvey asserts “You’ve gotta have a lot of ideas.” When one fails, you need to be ready to put another one into play. Throughout his career, Harvey was constantly putting an idea of evolutionarily-conserved circuitry up to the test; if it didn’t fly, the next theory was tested.

The last piece of advice, and perhaps my favorite quote from our conversation: “Make sure you take enough time off to remember that you’re a human being.” Harvey counts hours on his boat, the Night Heron, to be truly irreplaceable. “This [science] was another good thing to do, and in periods of my life it’s been the only thing, but that doesn’t mean it was the wisest thing… You’re a human being, enjoy that.”

Classic Harvey Karten readings

Karten, H.J. (1969). THE ORGANIZATION OF THE AVIAN TELENCEPHALON AND SOME SPECULATIONS ON THE PHYLOGENY OF THE AMNIOTE TELENCEPHALON. Annals of the New York Academy of Sciences. [PDF]

Karten, Harvey J., and William Hodos. (1967) “Stereotaxic atlas of the brain of the pigeon (Columba livia).” [Amazon]